Hydropower is one of the oldest forms of energy creation, and uses the flow of rushing water to create electricity. The province of Québec, Canada, has historically had an abundance of it and, later this spring, will start supplying hydropower to New York City.

This is the second big hydropower line to link Québec and the Northeast U.S. this year, after a line to Massachusetts came on board this winter.

Right now, the power is going one way, from Canada to the U.S., but some are thinking that the U.S. could eventually sell renewable wind energy back to Canada and let that country hold on to its hydropower for when it's really needed, creating a “regional battery,” says Marketplace's Henry Epp, who’s been reporting on this.